Project Summary/Abstract In its initial funding period, the ABCD consortium used a rigorous epidemiological approach to recruit a diverse sample of 11,878 9-10-year-olds through our 21 research sites, of which 2136 are twins or triplets. ABCD has created a comprehensive yet efficient protocol for participating youth and parents, using standardized and state-of-the-art methods for neuroimaging, biospecimens, and assessments of substance use, mental and physical health, neurocognition, culture, and environment, using a fully digital platform and making use of mobile technologies. We ensure cohesion and standardization by having employed a recruitment strategy designed by a professional survey company (experience with Monitoring the Future); standardized environmental, neurocognitive and mental health assessments, MRI assessments with all scanners using harmonized Human Connectome Project procedures, and computerized data collection with real-time quality control. Developmentally tailored assessments will have stable sensitivity and construct validity across the childhood and adolescent developmental period. They minimize participant burden, yet capture even subtle changes over time in substance use, mental health, neurocognition, development, and environment, and we employ novel state-of-the-art bioassays and passive data collection from mobile devices. A detailed retention plan builds on the experience and success of our investigators. This application describes the ABCD Data Analysis, Informatics and Resource Center (DAIRC), which will: maintain and update the harmonized MRI acquisition protocol, compatible with all major scanner platforms, taking advantage of recent technological advances in structural and functional MRI; perform rigorous quality control and quantitative calibration procedures to ensure accuracy and comparability of derived imaging measures across scanners and across time; implement advanced computational analysis workflows for all imaging data; implement reliable data entry, quality control, and monitoring tools for the substance use questionnaire, neurocognitive assessments, bioassay- derived measures, and mobile technologies assessment data; implement the state-of-the-art statistical analysis tools and procedures needed to integrate information across measures and modalities; continue development of infrastructure and procedures for public sharing of raw and derived data and associated tools and computational workflows; and enable interactive data exploration and analytics through a web-based Portal.